Metallic recovery system

ABSTRACT

A conversion system for waste having organic and inorganic components wherein the organic components are pyrolyzed in an essentially oxygen-free atmosphere so as to preclude the oxidation of the inorganic constituents. An afterburner provides the heat necessary for burning pyrolyzed gases and the carbonacious particulate matter produced in the pyrolyzing chamber. The pyrolyzing chamber is maintained at a suitable temperature for properly pyrolyzing waste material by tempering hot gases exhausting from the afterburner with cool ambient atmosphere, and then directing the mixed gases back over the pyrolyzing chamber.

United States Patent Hazzard et al.

METALLIC RECOVERY SYSTEM Inventors: Noel D. Hazzard; William M.

Anderson, both of Wellsville, N.Y.

Assignee: The Air Preheater Company, lnc.,

Wellsville, N.Y.

Filed: May 8, 1972 Appl. No.: 253,673

US. Cl. 110/8 A, 110/14, l10/49 R Int. Cl. F23g 5/06 Field of Search110/8 A, ll, 14,

References Cited UNITED STATES PATENTS 6/1958 Davis ll0/l4 X 1/1968Rodgers 110/11 X 7/1963 Lantz, Jr 110/14 1 Dec. 25, 1973 2,811,937l1/l957 Bouchard 110/49 X 3,303,798 2/1967 Kartinen et al. 1 10/1 1Primary Examiner-Kenneth W. Sprague Attorney-Wayne H. Lang etal.

[5 7 ABSTRACT A conversion system for waste having organic and inorganiccomponents wherein the organic components are pyrolyzed in anessentially oxygen-free atmosphere so as to preclude the oxidation ofthe inorganic constituents. An afterburner provides the heat necessaryfor burning pyrolyzed gases and the carbonacious particulate matterproduced in the pyrolyzing chamber. The pyrolyzing chamber is maintainedat a suitable temperature for properly pyrolyzing waste material bytempering hot gases exhausting from the afterburner with cool ambientatmosphere, and then directing the mixed gases back over the pyrolyzingchamber.

8 Claims, 1 Drawing Figure METALLIC RECOVERY SYSTEM BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to asystem for the thermal conversion of waste that comprises primary andsecondary combustion chambers wherein waste is pyrolyzed in the primarychamber to produce a gaseous exhaust that is burned by an afterburner inthe secondary combustion chamber. The exhaust from the afterburner isducted back over the primary combustion chamber to provide the heatnecessary for pyrolyzation.

2. Description of the Prior Art Incineration of waste material isfrequently carried out in a manner represented by U.S. Pat. Nos.3,491,707 and 3,547,056 wherein individually fired primary and secondarycombustion chambers pyrolyze the waste material and then burn thegaseous exhaust given off therefrom. The temperature in the primarycombustion chamber is usually regulated by controlling the oxygen flowfor combustion in such a manner that it regulates the rate of combustiontherein and thus the temperature in the combustion chamber. Inasmuch asoxygen for combustion creates an oxidizing atmosphere in the pyrolyzingchamber, the pyrolyzing of the aluminum or gold foil, circuit boards orphotographic film not only pyrolyzes the organic constituents of thewaste but it generates oxides of the metals which are given off asgaseous fumes so that the recovered metallic product is reduced both inquality and in quantity. Thus, conventional starved-air" typeincinerators are not deemed to be suitable apparatus where it is desiredthat residual metals be reclaimed for re-cycling or where pollution ofthe atmosphere be maintained at a minimum.

SUMMARY OF THE INVENTION It is therefore an objective of the presentinvention to provide a system wherein pyrolyzation of waste material iscarried out in a primary chamber that is maintained essentially free ofall oxygen so that excessive metallic oxides are not formed to destroythe quality and reduce the quantity of the reclaimed metallic residuenor are metallic oxides exhausted to pollute the atmosphere.

In accordance with our invention we therefore provide a recovery systemhaving a pyrolyzing chamber that is maintained essentially oxygen-freeso that waste therein is heated indirectly by the hot exhaust gases ofthe afterburner. The afterburner is adapted to burn all the gasesgenerated in the pyrolyzing chamber in addition to gas from an outsidesource that may be required to maintain a suitable temperature tocombust the gases being discharged from the primary or pyrolyzingchamber. The temperature in the pyrolyzing chamber is in turn closelycontrolled by tempering the hot gases exhausting from the afterburnerwith cool ambient atmosphere so that it is maintained at what may beconsidered an optimum temperature for pyrolyzation of the wasteinvolved. The pyrolyzation chamber comprises essentially a rotaryhearth'which is open at but one end for the loading of waste materialtherein and is heated indirectly so that there is insufficient air toprovide the oxygen enriched atmosphere necessary for oxidation.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE shows the schematicflow diagram of a waste reclamation system involving the concepts of thefollowing invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the single FIGURE of thedrawing the cylindrical drum l0 encloses a pyrolyzing chamber 11 that ismounted for rotation about its horizontal axis on a central shaft 12.The shaft 12 extends axially from an end wall 14 to a leakproof bearing15 in the end wall of housing 16 so that there is no leakage of ambientair into the housing 16. Shaft 12 is in turn rotated by means such asindicated by a variable speed motor 18. The opposite end of thecylindrical drum 10 is mounted on vertically adjustable outside supportbearings represented by numeral 20 whereby the drum 10 may be rotatedabout its. axis and simultaneously displaced slightly from thehorizontal so that the waste material therein is gently agitated andslowly moved away from the end wall 17.

The cylindrical drum has open end 22 opposite closed end 14 that extendsthrough an opening having an annular packing 24 in housing 16 and intothe opening in the afterburner chamber 28' that has an annular packing26. The bottom of chamber 28 opens into a hopper 32 for the collectionof residual matter being rejected from the pyrolyzing chamber whereby itmay be periodically emptied of its contents through closure 35.

The cylindrical feeder 36 having an open end 38 at one end and an endplate 46 at the other extends horizontally through a wallet theafterburner and concentrically through the drum 10. The feeder 36encloses a screw type device 44 that is rotatably mounted in a bearingat one end located in the center of end plate 46 and at the opposite endby a bearing in end wall 14. The screw is rotated slowly about its axisby a motor drive means 50 whereby waste material from hopper 52 beingadmitted to the feeder 36 is slowly moved laterally by the screw 44through the cylindrical feeder 36 to the open end thereof where it isdischarged into concentric chamber ll. Slow but continuous rotation ofthe cylindrical drum then causes the waste to move in a reversedirection toward open end 22 where it is discharged to hopper 32.

The drum l0 encloses a substantially airtight chamber 11 having no inletfor oxygen other than for oxygen that is entrained with waste materialas it is supplied through the cylinder 36. An air lock such as a starwheel 54 subjacent hopper 52 further limits the flow of excess airthrough the cylindrical feeder 36 to that which is normally entrained inthe waste material.

After being driven off from the organic waste in chamber 11, thepyrolyzed gas exhausts through the open end 22 of drum l0 and rises tosupply the afterburner 55 where it is totally consumed in accordancewith standard practice. Hot exhaust gases from the afterburner arecontinuously monitored by the thermocouple 56 having an indicator 57 andacting through controller 62 to maintain proper adjustment at valve 64which controls the supply of additional fuel and air from a source 66 sothat the gas is totally consumed by the afterburner. The controller 62is set to provide fuel and oxygen necessary to the afterburner toprovide 3 temperature in exhaust duct 72 at suitable levels rangingfroml,200 to l,600 F., the exact temperature depending upon the type ofwaste material being processed, the throughput desired, and theresidence time of the hot gases in unit 72.

l-lot exhaust gas from the afterburner exhausting through duct 72 issummarily directed over the outside of the cylindrical drum 10 so as tosupply the heat necessary for pyrolyzation of the organic waste in thechamber 11. Inasmuch as the temperature in chamber 11 must be sufficientto obtain complete pyrolyzation of the waste material but not excessiveso as to liquify the metallic wastes, the optimum temperature in thepyrolyzation chamber may vary from approximately 900 to l,l F.Therefore, the afterburner exhaust gases must be considerably cooledbefore being used. Accordingly, the cool ambient atmosphere ascontrolled by valve means 76 is fed into the afterburner exhaust throughan inlet 74. The valve 76 in turn is controlled by thermocouple 78acting through control means 80, while an indicator 79 at all timesshows the true temperature of gases within the duct. Inasmuch asmaintaining a suitable pyrolyzing temperature within chamber 11 is thepurpose of thermocouple 78, it may be accordingly placed at variouslocations within housing 16 or even within the pyrolyzing chamber 11 toobtain the most accurate and rapid response.

ln order that the temperature of the waste in the pyrolyzing chamber 1 1may be raised quickly to a. suitable pyrolyzing temperature, anauxiliary burner 84 having an independent source of fuel (not shown)controlled by valve means 86 is provided whereby the waste material inchamber 11 may be rapidly brought up to a suitable pyrolyzingtemperature. When such a temperature has been achieved the burner may beshut off completely and sufficient heat supplied by the heat in the hotgases from afterburner 28.

After the hot exhaust gases from the afterburner circulate over theoutside of drum and transmit heat to the waste material in chamber 11,the then cooled gases are exhausted through stack 88 to the atmosphere.

In operation the burner 55 is at first lighted to provide hot exhaustgas that flows through duct 72 to housing 16 and over cylindrical drum10 to the exhaust stack 88. After a buildup to the proper temperature,waste material including organic and metallic components is advanced byscrew feeder 44 through tube 36 to the interior of chamber 11 where therotation of drum 10 is instrumental in moving it laterally back towardopen end 22. As the material is moved slowly back toward end 33, it isindirectly heated by the hot exhaust gas from burner 55 to a temperatureof pyrolyzation whereby the gaseous constituents are driven off throughopen end 22 to mix with the flame of afterburner 55. As the pyrolyzedgas from chamber 11 supplements the gas from source 66, the thermocouple56 acting through controller 62 and valve 64 is instrumental inmodulating the fuel and air being supplied to the burner 55 in such amanner that as the pyrolyzed gas increases the flow of gas through valve64 is decreased thus maintaining a predetermined temperature in duct 72sufficient to effect complete combustion of the gases admitted to theafterburner.

While a temperature of from l,200 to 1,600 F. may be desirable in duct72 to obtain complete combustion of the fumes from afterburner 28, asomewhat lower temperature of from 900 to 1 ,l00 F. is desirable inhousing 16 in order that corrosion of the drum l0 and shaft 12 isretarded, and in order that metallic constituents of the waste materialin chamber 11 will not be reduced to a molten condition.

Accordingly bleed valve 76 is adapted to respond to thermocouple 78 tomaintain a suitable temperature in housing 16. Thus, if the thermocouple78 should sense excessive temperature in said housing, the valve 76 willbe moved toward open to allow a greater flow of cool ambient air and alowering of the temperature.

Inasmuch as the type of wastes, their chemical constituency andthroughput desired may vary widely, each burn should be inspected to seeif satisfactory results are being achieved. Thus thermocouple 56, forexample, be set at l,300 F. and thermocouple 78 at 900 F. forpreliminary operation. if observation of the metallic waste beingexhausted to hopper 32 should show the presence of non-pyrolyzed organicmatter, the temperature in chamber 11 may be increased by decreasing theamount of cool ambient air being introduced through duct 74. Moreover,the residence time of waste material in chamber 11 may be increased byslowing the speed of rotation of drum 10 or even decreasing its angle ofinclination'so that it is displaced from horizontal to a lesser degree.

While this invention has been described with reference to theaccompanying drawing, it is readily understood by those skilled in theart that such invention permits modification within the scope of theappended claim.

We claim:

1. A pyrolyzation system for the recovery of metallic residue from wastematerial that contains organic and metallic components comprising incombination a cylindrical drum with an open end and a closed endenclosing a primary chamber for the pyrolyzation of waste materialtherein, means for rotating the drum about its axis, means for supplyinga quantity of waste material into the open end of said drum, a secondarychamber, an afterburner in said secondary chamber, means supplying aquantity of fuel and-air to the afterburner, means directing gasgenerated in the primary chamber to the afterburner, and a passagewaydirecting the flow of hot gas exhausting from the afterburner over theoutside wall of the cylindrical drum whereby waste material therein isheated to a state of pyrolyzation by the transfer of heat in the gasexhausting from the afterburner to the atmosphere through the walls ofthe cylindrical drum. V

2. A system for the recovery of metallic residue as defined in claim 1including means cooling the gas exhausting from the afterburner tocontrol the temperature of the exhaust gas circulating over the outsidewall of the cylindrical drum thus regulating the pyrolyzation of wastematerial within the cylindrical drum.

3. A system for the recovery of metallic residue as defined in claim 2wherein the means for cooling the gas exhausting from the afterburnercomprises a passageway supplyingambient air to the gas exhausting fromthe afterburner, and means responsive to temperature of a mixture ofsaid ambient air and gas to control the flow of ambient air into saidexhaust gas.

4. A system for the recovery of metallic residue as defined in claim 1wherein means for supplying a quantity of waste material into thecylindrical drum comprises a tubular housing that extends concentricallythrough said drum.

5. A system for the recovery of metallic residue as defined in claim 4including a screw type feeder inside said tubular housing, and means forrotating said screw type feeder to deliver waste material through saidtubular housing adjacent to the closed end of the primary chamber.

6. A system for the recovery of metallic residue as defined in claim 5including a hopper arranged to supply waste material to the tubularhousing, and an air lock intermediate the hopper and the tubularhousing, and an air lock intermediate the hopper ant the tubular that isrejected from the open end of said drum.

1. A pyrolyzation system for the recovery of metallic residue from wastematerial that contains organic and metallic components comprising incombination a cylindrical drum with an open end and a closed endenclosing a primary chamber for the pyrolyzation of waste materialtherein, means for rotating the drum about its axis, means for supplyinga quantity of waste material into the open end of said drum, a secondarychamber, an afterburner in said secondary chamber, means supplying aquantity of fuel and air to the afterburner, means directing gasgenerated in the primary chamber to the afterburner, and a passagewaydirecting the flow of hot gas exhausting from the afterburner over theoutside wall of the cylindrical drum whereby waste material therein isheated to a state of pyrolyzation by the transfer of heat in the gasexhausting from the afterburner to the atmosphere through the walls ofthe cylindrical drum.
 2. A system for the recovery of metallic residueas defined in claim 1 including means cooling the gas exhausting fromthe afterburner to control the temperature of the exhaust gascirculating over the outside wall of the cylindrical drum thusregulating the pyrolyzation of waste material within the cylindricaldrum.
 3. A system for the recovery of metallic residue as defined inclaim 2 wherein the means for cooling the gas exhausting from theafterburner comprises a passageway supplying ambient air to the gasexhausting from the afterburner, and means responsive to temperature ofa mixture of said ambient air and gas to control the flow of ambient airinto said exhaust gas.
 4. A system for the recovery of metallic residueas defined in claim 1 wherein means for supplying a quantity of wastematerial into the cylindrical drum comprises a tubular housing thatextends concentrically through said drum.
 5. A system for the recoveryof metallic residue as defined in claim 4 including a screw type feederinside said tubular housing, and means for rotating said screw typefeeder to deliver waste material through said tubular housing adjacentto the closed end of the primary chamber.
 6. A system for the recoveryof metallic residue as defined in claim 5 including a hopper arranged tosupply waste material to the tubular housing, and an air lockintermediate the hopper and the tubular housing, and an air lockintermediate the hopper ant the tubular housing adapted to limitexcessive air flow into the primary chamber whereby waste materialtherein is heated in an atmosphere having a low oxygen content.
 7. Asystem for the recovery of metallic residue as defined in claim 6 havingthe cylindrical drum displaced from its horizontal axis whereby rotationof said drum will advance the waste material therein toward the open endthereof.
 8. A system for the recovery of metallic residue as defined inclaim 6 including a hopper subjacent the open end of the cylindricaldrum adapted to receive residue that is rejected from the open end ofsaid drum.